The present invention is directed, in general, to integrated circuit metrology and, more specifically, to a probe having a nanotube stylet and to a method of manufacturing and mounting same for use in integrated circuit metrology.
A conventional stylus nanoprofilometer employing a probe stylet of quartz or diamond may be used to measure integrated circuit features down to approximately 100 nm line width. However, below 100 nm line width features, i.e., at about 80 nm, problems are encountered that are aggravated by the length and diameter of the probe stylet. A conventional quartz stylus has a Young""s Modulus of Elasticity of approximately 70 gigapascals (GPa) [1 GPa=1xc3x97109 Pa]. As feature sizes continue to shrink, the l3/r4 portion of the deflection equation degrades, forcing a major change in the Young""s Modulus required of the material being used.
One promising material form that could substitute for quartz, yet has a higher Young""s Modulus than quartz, is the carbon nanotube. Carbon nanotubes were discovered in 1986 as a discharge material byproduct from a carbon arc. They are actually sheets of graphite where opposing edges have become attached to each other creating a tube. They have exhibited extraordinary material properties including a Young""s Modulus approaching a terapascal, i.e., 1 terapascal=1000 Gpa=1xc3x971012 Pa. However, no material is problem free, and in the case of carbon nanotubes, the problems are associated with orienting and manipulating them due to their extremely small size. While carbon nanotubes may range from approximately 5 nm to 100 nm in diameter and from about 500 nm to about 5000 nm in length or longer, by their very size, manipulating and orienting them becomes a problem.
Nanotube material is now commercially available having diameters of ranging from about 10 nm to about 80 nm. A diameter nominally smaller than the feature size is preferable for probe stylets. Slightly larger or smaller diameter nanotubes can also be used depending upon the semiconductor technology, i.e., feature sizes of 160 nm, 120 nm, or 100 nm, etc., being investigated. Carbon nanotubes are extremely hard to manipulate and therefore, to orient, to tolerances within less than about 10 degrees to 20 degrees of the angle desired. While some efforts have been made to use a carbon nanotube as a probe tip for atomic force microscopes, all nanotube-based probes have heretofore been manufactured by attaching a carbon nanotube to an existing probe body by fastening the nanotube tip with an adhesive to the probe body tip. The method, in some cases consists of projecting the nanotubes against a probe body tip and literally hoping that one sticks in the correct orientation. The problem with this procedure is clearly in orientation, reproducibility and cost. For integrated circuit metrology, this is totally unacceptable due to common features having sidewalls within 1 degree of normal.
Accordingly, what is needed in the art is an alternative probe having a microstylet suitable for measuring semiconductor features having on the order of 160 nm or less line widths, and a method of manufacturing the probe.
To address the above-discussed deficiencies of the prior art, the present invention provides a probe comprising a probe body having a body longitudinal axis and a shoulder, and a microstylet mechanically coupled to the shoulder, and a method of manufacturing the same. In a preferred embodiment, the microstylet extends from the shoulder and has a microstylet longitudinal axis coincident the body longitudinal axis with the microstylet having a cross section substantially smaller than a cross section of the probe body.
Therefore, the present invention incorporates the positive attributes of a material having a higher Young""s Modulus and extremely small diameter, while dispensing with the problems of manipulating and attaching such a small particle to a probe body in an exact orientation.
The foregoing has outlined preferred features of the present invention so that those skilled in the art may better understand the detailed description of the invention that follows. Additional features of the invention will be described hereinafter that form the subject of the claims of the invention. Those skilled in the art should appreciate that they can readily use the disclosed conception and specific embodiment as a basis for designing or modifying other structures for carrying out the same purposes of the present invention. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the invention.